Two new large wetland areas are taking shape on the Great Fen. Work on Rymes Reedbed began in 2011 (lots of details here) and work on Kesters docking began in 2014.
In 2013, with the major construction work on the northern part of Rymes Reedbed under way, the Great Fen restoration team turned their attention to an adjacent area on its northeast side. Of a similar size to Rymes (170 ha), this area had also been part of Holme Lode farm and was acquired in 2007 following a major Heritage Lottery Grant. After the end of the farmer’s tenancy, the arable fields were sown with grass seed so that the area could be grazed by sheep and hay crops taken off. In the days when it was farmed, the formerly rich peat soil had been increasingly fertilised so the grass-growing regime started to remove these excess nutrients from the ground. It also helped to improve soil condition and reduces loss through fen blow.
This area is low lying (2-3 m below sea level) and is therefore most suitable to for wetland creation. It was known to have been on the western edge of the historical Whittlesea Mere (see details here) and a chart of the mere dated 1786 shows this area marked with the name Kester’s Docking ( an extract of the map is shown below. Presumably, this referred to a harbour or landing place used by the many boats that are known to have sailed the mere in the 17th and 18th centuries. Nothing is currently known of Kester except that he or she must have had landing rights to the land, but it seemed appropriate to resurrect this historical name and use it to describe this area of the Great Fen.
Extract from Chart of Whittlesea Mere, 1786 showing Kester's Docking and also Rymes Reedbed
The Kester’s Docking area includes two soil types: there is some of the last remaining deep peat in the area (formerly the edge of the mere) and also silty deposits from the bed of the mere itself. Post drainage, the peat contracted more than the silt, leaving the former mere now slightly higher than the area around it. Therefore physical and ecological studies indicated that Kester’s Docking would be most most suited to a mix of reedbed, open water, wet grassland and dry grassland.
The detailed design and supervision of construction went out to tender in 2013 and Wildfowl & Wetlands Trust (Consulting) Ltd (WWT Consulting) were contracted.
They were asked to produce a plan that would incorporate the following:
The consultants began by carrying out a feasibility study to assess whether it was all possible. They needed to answer such questions as:
This is not the place to describe all of these issues but the answers to those questions marked * are below.
A review of existing ecological data was undertaken with reports supplied by the Wildlife Trust in relation to Rymes Reedbed and the wider Great Fen restoration, liaison with the Great Fen Monitoring Officer and use of the National Biodiversity Network (NBN) database. This historical data suggested that Water Voles could well be present in the agricultural ditches so it was important to carry out a full survey. This was completed during the summer of 2013 by an accredited professional ecologist.
The survey found that there could be as many as 34 individual territories on the entire Holmelode Farm site, with signs of Water Voles mainly in those ditches that held water during the summer months. The map below shows all the ditches on Kester’s Docking marked in black, with those without signs of Water Voles shown dashed.
Other protected species were recorded close to, but not within the Kester’s Docking area. These included Badgers, Otters, Common Pipistrelles, Great Crested Newts, the nationally scarce Variable Damselfly and Scarce Chaser Dragonfly, the vulnerable Reed Leopard Moth and Swallowtail butterflies, which have both been recorded at Holme Fen.
LiDAR is remote-sensing technology that is used to make high-resolution maps of all types. To create a map showing ground height, LiDAR instruments are fitted to aircraft and satellites and are able to measure distances by illuminating a target with a laser and analyzing the reflected light.
The available LiDAR map is shown below. Lowest lying areas are shown blue, higher levels are shown green merging to yellow. Kester’s Docking is the area outlined in red and it is interesting to compare ground heights with those of Holme Fen (edged black) and other areas. It was necessary to “ground truth” these height data using GPS technology and to record topographic profiles of the existing ditch features. Spot heights were up to 40.5 cm lower than the corresponding LiDAR data. This could be due to errors in the equations used to interpret the LiDAR data, but also reflect ongoing soil loss since the LiDAR data was collected.
A process called water-budget modelling was used to answer this question. Using historical weather data the probable amount of water from rainfall (a plus in the budget) can be set against likely evaporation (a minus in the budget). So, for example, in January the probable gain is +47mm (48mm of rain and just 1 mm of evaporation) whereas in July the figure is -48mm (+56 – 94). Other factors such as surface run off, groundwater discharge, inundation from the ditch network were all factored in, as were the amount of water needed or provided by various types of wetland habitats. For example, 1 ha. of reedbed would require nearly 1600 cubic metres of water every year, whereas I ha. of open water would provide about 650 and wet grassland about 500.
Using these figures and taking into account the possible changes to climate in the future, it was possible to calculate the area of each type of habitat that could be sustained.
Wildfowl & Wetlands Trust (Consulting) Ltd have produced a most interesting concept plan incorporating:
The plan can be seen on this page. A planning application was submitted to Huntingdonshire District Council in May and approved in July 2014. The construction began in the autumn. Re-wetting will then be phased over 3-5 years to allow peat and soils to maintain/develop structure.